Just my observations...

I always though the Trijicon RMR, mini-RDS, was not a "serious" optic. Maybe piggy back on an ACOG or on a pistol for someone with poor eyesight. And for around the same retail price ($600) as a T1/T2 it didn't seem like a good option.

Then that Cabela's deal came along and I got the LED RM01 (Gen 1) with the 3.25MOA dot just to try it for $260 delivered with 2 mounts. It sat around unused for a while since I have no pistols or shotguns that could mount the RMR. I have Aimpoints and ACOGs on most rifles but I figured I'd mount it on my AR pistol using the free UTG mount that came with the RMR and see how it works.

My observations:

The dot illumination is auto-adjusting and works very well. I walked around my house, from dark to bright, looking from a dim room aiming outside into bright sunshine, "clearing" rooms using a WML. The dot was always very bright and visible. It never washed out no matter how much I tried. It seemed magical, instantly dimming or brightening depending on the ambient light. The dot was also very clean with very little bloom. Doing this with my Aimpoint, EOTEC etc, I would have to constantly adjust the brightness manually or probably leave it on a high setting and deal with the bloom in dark areas so the dot doesn't disappear when I hit the WML or go into a bright room. The RMR does this automatically and efficiently.

It worked very well at the range also. It's very easy to zero. I just co-witnessed with the irons then make some minor adjustments to get it dead-on at 50 yards.

I was so impressed that I ended up ordering a second RMR, this one with the 6.5MOA dot. I thought maybe I'll try the bigger dot if I mount it to a shotgun or pistol. But again, I mounted the 6.5MOA RMR on the AR pistol again just to try it. I assumed that the 6.5 dot would be too big for an AR but it was fine. The 6.5 dot is very clean with no bloom. It appeared perfectly round! (I wish my Aimpoint dots were so clean, but to see a 2MOA dot, I have to increase the brightness, thereby increasing the bloom) Side by side, the 6.5 dot appeared to be just a hair less bright than the 3.25 dot, but the bigger dot was quicker to pick out and was a cleaner, perfect circle with less bloom then the 3.25. Again, the auto adjusting brightness worked perfectly and I couldn't get it to fade or wash out. I was able to make accurate groups out to 100 yards.  

I can't decide which I prefer on an AR, the 3.25 or the 6.5MOA dots. If I could keep only one, I'd keep the 6.5 since it is very versatile, perfectly usable on an AR as well as a shotgun or pistol.

The battery should theoretically last 4-5 years on the lowest setting (when the sight is stored in a gun case, trunk, or safe, it will auto adjust to the lowest setting). On a high setting (ie you keep it in a bright area such as the gun rack in a patrol car) it should last 2 years. Replacing the battery every year should be plenty. And again, it co-witnesses well with irons, just in case.

What are some other opinions of using the RMR as a primary optic?

I recently got an rm02 for a glock 19. I've only had it for a few days but I don't think it is for me, so I am very interested to see what others are doing with their RMRs.

I put my RMR-06 on my AR-Pistol, and a copycat even less expensive Vortex Venom 6MOA on my AR-9 for USPSA.  Seems to work for me.

I run a 6.5 MOA on my Glock. I change the battery on my birthday and it's never been dead when I changed it.

Well, my experimentation with the RMR as a primary optic on an AR has hit a hurdle...

I took the rig out today (RM01 on AR pistol) and after my 2nd shot, it went dead. No dot!!

Luckily I had the little torx wrenches and took the RMR off it's mount. It was on nice and tight and the battery was in properly. I took the battery out, put it back in and re-mounted the unit. The dot was back on.

Since it had worked perfectly before and the unit was mounted up nice and tight, I don't know what could have caused it.

I want this type of set up.  And have for a while.  And wow that was a steal at 260.  I'm totally jealous.  

Although I've been thinking about going the Burris FF3 route, but I don't think that auto adjusts like you're talking.  Does the Vortexx?

no

I went FF3 route and have the 3.25 moa RMR now.

Go straight to RMR, the on/off on the FF3 is a major weak point IMO.

i own the dual for a piggy back on an acog and would not want it as a primary

a shooting buddy had a LED version on his acog and i could use rhat as a primary

The original RMR's were plagued with the "flicker" issue. Basically, the battery connection would be interrupted due to recoil. I loved my earlier RM06, but eventually moved on due to the issues. I'm now running a new Type2 and have had zero issues.

If you like RMR for a primary on an AR, or think you might, take a serious look at the duty grade, ruggedized, motion-activated Leupold Deltapoint Pro.  Much larger 28mm window.  Virtually tintless, very clear optical quality glass.  Top loading battery, making changing easy without resighting (although I'm 2+ years on original battery).  Leave it on 24/7.

I use a Insight MRDS on one of my set ups I love it and they have a lifetime warranty

I had to use the warranty after killing one on my glock , it was also used on a AK it’s been piggy backed on top of a scope on a .308 AR which it’s been awesome on

Warranty service was excellent no questions asked other then what’s the serial #

The insight mrds sucks for pistols because of the location of the buttons but on a rifle it’s awesome if you like it I would run it on a set up

My fav red dot is still my Aimpoint Comp M4

For me, the RMR type sights are okay on something you only want to shoot a "big" target with.

I don't really pay any attention to lens size/shape/color anyway.  My eye goes to the dot and is the dot on the target?  

I have a DP Pro on one of my AR15 pistols and it works fine.  I'm not sure I'd be happy with it on a carbine/rifle since I've never been happy with an aimpoint or other red dot type sight on a rifle.  I always (always) shoot better groups with a scope.  I have bought a few scopes these last few years that have an illuminated red dot in the center of the cross hairs.  That works okay for me.

We have a couple DP Pros.  One on that AR15 pistol and one on a CZ 75 Compact (my wife's pistol).  So far, no battery issues.  They are left on all the time.  The movement switch shuts them off after they are put away and turns them on when you grab one of them and move it.

My RMRs are the dual illuminated models, so no batteries required and those are on handguns.

I mounted the DP Pro out on the handguard.  Did that to put it farther out from my eye, like it would be if it was on a standard handgun.  No issues so far, but then I don't do mag. dumps either.

After it went dead briefly, I called Trijicon. They said they would be happy to look at it but suggested I change the battery first.

I took a closer look at the battery and I think it was probably the cause. It's an older Rayovac CR2032 battery that I had lying around and had a concave "+" side. This side goes face down and needs to contact a little lead inside the RMR. I'm thinking that due to being concave, it had a less than perfect contact with the lead. I replaced it with Duracell which is convex and should have a more positive contact. So far no issues after several range sessions.

Now I guess I have to try the RMR in the rain. And maybe a sandstorm (not common here in FL)...

The controls on the LDP suck.

Try the anti-flicker sealing plate from battlewerx. That will likely solve the issue.

I've been fighting irons for the last 5+ years. Eyes are going south (along with a few other parts) at 67 yrs young. M1 Garands, carbines and M14's are my thing & was getting so frustrated with irons
I almost tossed in the towel.....until I found out about the Hopco mount. I'm using a 3.25 moa RMR. 30.06 recoil doesn't phase it a bit. It's been awesome.
Here's a YouTube:
RMR on Garand

I love my RMR, but the fact of the matter is dust and dirt is ALWAYS getting in the emitter and I'm sick and tired of specks appearing on the reticle and having to blow it out. I've kept an RMR on my M4 (Benelli, not Colt) because it's like God's perfect shotgun optic with the Scalarworks mount, but I have switched to Steiner's MRS for carbine use and it's my new favorite lightweight reflex sight. About the size and weight of an RMR with a low mount, does not need to be removed to swap the battery, very rugged, and totally enclosed so junk never gets in the emitter. Also markedly less tint and distortion.

I have  Gen 1 RMR in one of Trijicons wing mounts.  They don't make the wing mount anymore but it has been on my rifle for several years and works great.  The sight has never failed me.

What controls?  I assume you mean DPP, Deltapoint Pro. The windage and elevation are very distinct.  They lock and are left alone.  The battery lasts years and is top loaded, so zero is never lost.  The intensity is typically set to one level and left alone.  It returns to the last setting when picked up.

If you are changing intensity all the time, you are doing something wrong.  If you need to, the button cycles smoothly.  It is placed where it will not be accidentally bumped in operation. You do not want that to change easily.

I have an RMR mounted on my Ruger MKIII Hunter and love it. When I have the money I am going to get a Gen5 G19 and have an RMR put on it. I think when it is on a pistol it is right there in your face.

My buddy has an AK with an RMR on it. I run ARs with Elcan DRs on them. I found when shoot drills the size of the Elcan helped as it was right there, easy to pick up. I had to kind of look a little for the RMR.

Maybe this is just a training/time on the weapon issue but this is what I ran into.

YMMV